Simulated flight control loading and centering means for grounded aviation trainers



K. A. KAlL 2,485,291

Oct. 18, 1949.

- SIMULATED FLIGHT CONTROL LOADING AND CENTERING MEANS FOR GROUNDED AVIATION TRAINERS 5 Sheets-Sheet 1 Filed June 27, 1945 flumunuuu 2; f unnununnu KARL A. KAI L INVENTOR.

. 'ATTORN s Oct. 18, 1949. KIA. KAlL 2,435,291

SIMULATED FLIGHT CONTROL LOADING AND CENTERING MEANS FOR GROUNDED AVIATION TRAINERS Filed June 27, 1945 5 Sheets-Sheet 2 Oct. 18, 1949. K. A. KAIL SIMULATED FLIGHT CONTROL LOADING AND CENTERING MEANS FOR GROUNDED AVIATION TRAINERS 5 Sheets-Sheet Filed June 27. 1945 FIG. 2B

KARL A. KAI L IN VEN TOR. WW

FIG.2E

ATTORNE Oct. 18,1949. K.-A. KAlL SIMULATED FLIGHT CONTROL LOADING AND CENTERING MEANS FOR GROUNDED AVIATION TRAINERS 5 Sheets-Sheet 4 Filed June 27, 1945 NNN mmN

at v Qmw\ Oct. 18, 1949. K. A-. KA L l SIMULATED FLIGHT CONTROL LOADING AND CENTERING 5 Sheets-Sheet 5 MEANS FOR GROUNDED AVIATION TRAINERS Filed June 27, 1945 3 g 2 E g N p \Q' 3 1 2 O 3) L:

KARL A. KAIL INVENTOR.

17% ATTORt- EY Patented Oct. 18, 1949 UNITED STATS OFF ICE Karl A. Kail, Montrose, Pa... assignon to Link Aviation Inc., a corporation of New York Application June 27, 1945,- SerialNo. 601,77'6' 21 Claims.

Ihis inventionrelates to the provision of means for simulating in agroundedaviation trainer the operation and responses'of certain of the flight controls in actual aircraft.

The preferred embodiment of my invention willbe illustratedin conjunction with a grounded aviation trainer of the type manufactured by Link'AviationDevices; Inc., of Binghamton, New York; For thegeneral'oonstruction and operation of such trainers reference-is made to U. S. Patents 1,825,462- and 2,099,857.

In the case of actual aircraft in flight the slipstream places a' load on the control surfaces (ailerons, elevator and rudder) which resists the movement of the control surfaces from their neutral position; Inasmuch as the control surfaces are connected to the flight controls (wheel or stick and rudder pedals) within the cockpit which the pilot manipulates t'o movethe control surfacesin order to change the attitude of the plane about its three axes, when the control surfaces are in their neutral'positions, the controls are similarly positioned. Thus when the pilot moves any one of the controls from its neutral position, the slipstream effect upon the control surfaces produces a force which resists the movement of the control from its neutral position. This force is commonly referred to in the art as control' loading.

Itis a main object of this invention to provide novelmeans whereby a load may be placed upon the simulated controls in a grounded aviation trainer when the controls are moved from their respective neutral positions.

Further, in the case of planes in actual flight, if any one of the controls is moved from its neutrad position:the associated control surface is at the sametime displacedfrom its neutral position. Then, if the control is released, the force of the slipstream upon the control surface connected'to the control returns the control surface to its neutralposition; and the control is simultaneously returned'to the neutral position with the movement of the control surface.

It is a further object of my invention to provide novel'means in a grounded navigation training device for returning the simulated controls to their respective neutral positions when they are moved from their neutral'positions andreleased'.

As disclosed'in the two above mentioned U. S. patents and'as' is well'known to the prior art, in trainersof the type in connection with which my invention will be illustrated there are provided three-main controlvalves referred to as the rudder valve; elevator valve and aileron valve. The ruddervalve is connectedto the simulated'rudder CONTROL LOADING 2 pedals inthesimulated fuselage so that when the rudder pedals are moved from their neutral positions thefuselago properly turns to the left or right; according to the position of the rudder valve.- Also, when the simulated'control column or stick is moved'ahead or to the rear of its neutral position, a connection between the stick and elevator valve operates the elevator valve so that the fuselage will assume the proper diving or climbing (pitching) attitude. Further, when the simulated control wheel or stick is moved in simulation of the manner in which the stick or controlwheel in a real plane is moved to bank the plane; a connection from the control wheel or stick to the aileron valve moves the valve so that the 'simulated'fuselage assumes a proper banking position.

It. is a further object of my invention to comblue in a trainer of the type illustrated structure arranged to accomplish. the abovestated objects of my invention. combined with the rudder, elevator and-aileronvalvesof such trainers, so that the controls are not only properly loaded when they are moved from a predetermined neutral position,- and. returned to the. neutral position when'the manual pressure thereupon is released, but also so that the fuselage is properly turned, pitched'and banked according to the movements of the simulated flight controls.

In order. that the preferred embodiment of my inventionv may be clearly understood, reference is made :to :the' accompanying drawings wherein like charactersdesignate like parts. In the drawings,

Fig.1 is a generalview of a grounded aviation trainer of the type being considered showing the general location of many of the major parts of this invention.

Fig. 2is-a detailed perspective view of the elevator control loading'system, together with the elevator trim-system.

Fig. 2A isa detailview showing the construction of the=elevatorand aileron control loading bellows.

Fig. 2B is'a' detailed exploded View of a typical control loading centering valve which may form apart of my invention.

Fig. 2C isa detailedshowing of a typical control' loading regulator bellows.

Fig. 2D is a detailed showing of a compensating spring arrangement which may be used in the practice of my invention.

Fig; 2E'isa detail view of the cam arrangement shown generally in Fig. 2.

Fig.3 is a detailed showing of the aileron control'loading andtrimming means.

Fig. 3A is a detailed view of the cam arrangement shown generally in Fig. 3.

Fig. 4 is a detailed showing of the rudder pedal loading and trim system.

Reference is now made to Fig. 1 which is a general disclosure of grounded aviation trainers of the type covered by U. S. Patents 1,825,462

and 2,099,857. Such trainers comprise a stationary base "ill above which is mounted a fuselage i2 simulating the fuselage of an actual aircraft. Within this fuselage there is a seat for a student positioned to the rear of the control wheel 30. The fuselage l2 rests upon a universal joint l4 and this joint is sup-ported by the main central vertical spindle iii which is rotatably held by the stationary base ii). The conventional or:- tagon is designated by it and as is well known to the prior art, octagon i6 is aflixed to the main spindle l5 below the universal joint l4 by means of suitable horizontal arms so that the octagon l5 rotates with the spindle l5 and fuselage 12 relative to the stationary base H A forward pitching bellows Ill and a rearward pitching bellows it are provided, the bottom portions of each of these bellows being affixed to the arms which hold the octagon l6 relative to the vertical spindle i5, and the upper ends of these bellows are afixed to the bottom of the fuselage i2. These two bellows lie in a vertical plane through the longitudinal center of the fuselage H2. Upon the admission of vacuum to the forward bellows ll and atmosphere to the rear bellows [8, the former bellows collapses and the latter expands causing the fuselage [2 to assume a diving attitude. On the other hand the admission of vacuum to the rear bellows l8 and of atmosphere to the fore bellows l 1 causes the fuselage l2 to assume a climbing attitude. As will be more fully explained later, the admission of vacuum and atmosphere into the bellows II and i8 may be controlled by the student in the trainer by moving the control wheel 30 fore and aft of the fuselage If, so that the student may control the diving and climbing position of the fuselage [2. The diving and climbing position of the fuselage are sometimes referred to as pitching.

At the same time trainers of this type have a left banking bellows H] as well as a right banking bellows 28 upon the opposite side of the universal joint M from the bellows [9. The admission of vacuum and air into these bellows may be controlled by the student through a rotation of the control wheel 33 so that he may place the fuselage l2 in any desired banking position within the limits of the apparatus.

Trainers of the type being considered are often equipped with a stick instead of a control wheel, and it will be readily apparent to those skilled in the art, after reading this application, that they can substitute a stick for the wheel 30 and still obtain all of the advantages of my invention.

Fixedly carried by the octagon I6 are the horizontal arms H which support the turning motor 22. By means of a well known pulley arrangement connecting the turning motor 22 with the stationary base it, the student in the fuselage l2 may, by pressing either of the rudder pedals 2 55, energize the turning motor 22 in such a direction that the turning motor 22, supporting arms 2|, octagon l6, bellows I1, l8, l9 and 25, spindle l5, universal joint I4 and fuselage l2 will rotate either to the left or right, as desired, relative to the stationary base It. Thus the student may control the simulated heading of the fuselage l2 in the same manner that he would control the heading of a plane in actual flight. The arms are are attached to the octagon l6 and support the housing 2lb in which may be placed a vacuum pump for operating the instruments in the trainer, as is well known in the prior art.

The steps 25 and door 26 allow access to the interior of the fuselage l2 and a slidable canopy 27 may be used to completely encompass the cockpit of the fuselage E2 in order to simulate blind flying conditions. The canopy 27 may be made of a suitable translucent material in order to permit enough light to enter the cockpit of the fuselage to enable the student to manipulate the trainer without the assistance of artificial lights placed in the interior of the fuselage. Such conditions closely simulate day-time blind flight conditions. On the other hand when it is desired to simulate night-time blind flying conditions, a suitable opaque material such as a cover may be placed over the canopy 21 in order that no light enters the cockpit through this canopy. The student must then rely upon the conventional artificial lights which are placed inside the cockpit. Such an arrangement closely simulates night-time blind flying conditions.

An instrument panel 29 is inside the fuselage and upon this panel are instruments which simulate the instruments carried by actual aircraft. As is well known to the prior art, these instruments operate in response to simulated conditions just as the corresponding instruments in a real plane react to real flight conditions.

Simulated elevator control loading and trimming means Referring now to Fig. 2, it will be seen that the control wheel in the fuselage is designated 30 and that this wheel is fixedly mounted upon the rear end of the forwardly extending shaft 32. As will become clear later in the description, the fore end of the shaft 32 is mounted in a bracket carried by the fuselage so that the shaft 32 may move axially. A pair of collars 34 are amxed upon shaft 32 as shown so that axial movement of the shaft 32, caused by the student's pushing or pulling the wheel 30, results in a pivoting of the upstanding members 38 which are pivotally mounted at their lower ends upon the horizontal transverse shaft 40 which is fixedly held by the bracket 42 mounted upon the floor of the fuselage as seen in Fig. 1. The upstanding members 38 are positioned with respect to one another by the crosspieces 44 and 46.

In Fig. 2 it will be seen that integral with the fixed bracket 40 are a plurality of upstanding members 48 which support a base plate (not shown) to which are attached the fixed, vertical, bellows supporting plates 50, these two plates being parallel and placed upon opposite sides of the elevator control loading bellows designated generally by 52.

Reference is now made to Fig. 2A which is a detailed disclosure of the construction of the bellows 52. In Fig. 2A it will be seen that the bellows 52 comprises a pair of end members 54 which are fixedly held by the plates 50 by means of screws 55. In the center of the bellows 52 is the main, generally upstanding, common bellowsforming member 56 pivoted at its bottom end by means of the rod 51 held by the plates 50. It will be seen that between the member 56 and each of the end members 54 is a rigid wooden member 58 each having a plurality of holes 59 therethrougm 'I wo substantially=airproof, fieX- ible coverings 60 are.-provided,.one on either side of-themember: 5B and'attachedlthereto; In view of: the; described arrangement. it. willbeappreciated: that thebellows 52 in. reality comprises two separate bellows; eaehi-havingone. fixed end in theformaofz its associated member S t and each havinga common =1novablecentral member. in the. form-of the member 55. The left bellows seen inlFig; 2A is designated 52a and is connected through the port. 61. and air-vacuum line with the-threefleaf elevator centering -.valve designated generally by 63.. The right bellows in Fig. 2A is: designated 52b 7 and is connectedithrough port Maandlvacuum-air line 65wwith the-elevator centering valvefiS-z Reference:is-now-madeto. Fig. 2B which shows thezdetailedx construction of theelevatorcentering: valve 63;. Asseen, this valve comprises a lowen fixedrleaf 6.6; a center movable. leaf 6? and anupper'movablexleaf. 68;. Referring" to Fig.2 itlwilllbeeseen that the lower fixed leaf Btis affixed; to the bracket' slii which in turn is afiixed ton thee plates-10.; and- H' which are aflixed to the stationaryside; plates .50. Consequently the lowerleaf: dfiiisifixedlin relation to the interior of the fuselage: l'2.'.

ReferringtolEigzzB, it willbe seen that fixedly monntediintheacentenof'thelower leaf 66 is the verticalhollowstem 12 having a plug 73 in its of theelevaton controlzlo'ading. regulator bellows designated generally 14'. The bellows M'shown in detailiin Fig; 2C compriseszalower fixed member: 15- and an upper member 16' pivotally at.- tachedthereto. A suitable flexible, airtight cov ering H is provided. Attached to the upper.- pivotedmember'lS-is-the plate 16a towl'iich the lower en'd'iof thespring' I21 is connected. Fixedly at tached to: the upper bellows member 16'- is the needle 19 and aseat" Bil-is affixed to'= the lowermemberTSZ Seat 80 is connected through the vacuum line 8 I 1 to the airspeed regulator bellows. shown in: Fig. 2 and designated generally 82-; Theairspeed regulator bellows is connected by vaeuum line 83- to the well known turbine 84 shown in' Fig;.l'..

Asxis-wellknown in the priorcart, the airspeed regulator bellows 82,.loca-ted.shown in=Fig. 1, is: responsive to the climbing:and diving'movements :of the fuselage'lzas wellas to the movements of the throttle lever conventionally found.

ini trainers-ofv the type being. considered; Eor presentpurposes: itisi-sufiicient to .know that the pressureawithin the airspeed regulator. bellows8'2.

is atrallitimes inversely related to the assumed airspeed of the fuselage. For convenience it may hestated'that the higher the assumed airspeed,.

the greater 'isithe vacuum within the'bellows 82;

Still; referring: to Fig. 2, the vacuum within bellowss'az:manifestszitself at. all timesin the cen trahstemflZ of the lower. fixed leaf 66 'through' the vacuumlinerlfl, elevator control loading regulatorrbellows" l4 and;vacuum. line 13; but asawilll later: appear the. bellows .14; controls the 1 amount of vacuum in:stem 12.

Referring to. Fig. 2B.itwill-be seenthat axpair oflvertical ducts 85- and Bit-extend from the upper face of: leaf. 66." downwardly and partly through theileaf: 6.6. Connecting with'the duct 8545- the exterior portu85a which connects with the line &5 which, as:seen-in;Fig. 2, connects. with the rightfbel-lowsfifllrof the bellowsassembly '52 Sinie ilarly, connecting withzthe ductcBBzisthe. port; 8.11 which. connects with. the. line 62. which. connects with theinterior of thebellows 52a of the. bellows assembly 52';

Referringagainto'l lig. 23, it will be seen that the movable; cent'en leaf 6'! has a central bore 88 adaptedzto receivethe vertical. stem 12 and that: twoports 89. and .90 extend'completelyt through theleaf. 61. When the leaf 61 is-assenibled relative to-the lowerzfixed leaf 66,,leaf 61 beingin. the central or neutral'position, the port.8 9:coincides exactly withthe. portt and the port 96 coincides exactly withitheport 8B.

In the upper movable leaf; 68 are a pair of vertical ducts HI and 92 which extend completely. through theleaf 68; It will be appreciated that the upper! ends of both of the ducts 9| and 92 are at; all times connected with the atmosphere. Centrally located within the leaf 63 is the vertlcal boreeaextending completelyv through leaf. 68 and adapted to receive the stem 12 of the lower leaf. Communicating. with the vertical bore 93 of leaf 68 is the transverse duct 94 which communicates with the vertical. duct 95 drilled inthe lower 'face of the leaf 68.

When the three leaves of the valve shown. in" Fig. 2B are in the neutral assembled position, it will. be appreciated that the: vacuum in. the

stem IQ-passes throughthe'ports l-iin the stem between the ports 9! and- 89 on the one-hand and ports92 and on the other. Consequently, when the leaves of the valve 63 are all in-theirneutral position, a slight amount of vacuum passes through the lines 62 and65 into the bellows 52a and 52b, and the bellows are neutralized.

However, assuming that the upper leaf 58 is rotated counterclockwise from its neutral position, it will be appreciated that the vacuum port will engage the port $9 which in the neutral position engages the port 85 of the lower leaf 65. At the same time the atmosphere port 92 will engage the port 90 which in the neutral position engages the port 88. Consequently, an increased amount of vacuum will be applied to the line 65 which connects with the interior of the bellows 52b and simultaneously atmosphere will be applied through the line 62 to the bellows 52a. The

bellows 5 b will therefore be contracted andthe bellows 552a will. expand. The common. central member liiiwill have aforce applied thereto tending to move it to the right in Fig. 2 and by means of the clamping arrangement 5? and rod as. the upper ends of the members 38 will tend The shaft 32 and wheel at will have a force appliedin the same direction.

On the other hand, it should be understood.

without a detailed explanation that when the three leaves of the valve Share in the neutral position, a clockwise movement of the upperleaf 6% willapply increased vacuum to the bellows.

52a and atmosphere to the bellows 52b. The. commonacentralmember 56 willhave a force ap plied theretotending'to move it to therear. of:

the fuselage, and the shaft 32 and wheel 39 will have a tendency to move in the same direction.

Further, assuming that the leaves are in the neutral position and that the upper leaf 99 is moved counterclockwise to admit increased vacuum to the bellows 52b and atmosphere to the bellows 52a, it will be appreciated that a corresponding counterclockwise rotation of the center leaf 6'! will shut off the passage of increased vacuum to the bellows 52b and will, at the same time, shut off the passage of air to the bellows 52a. The vacuum leak through the leaves when they are neutrally positioned will quickly neutralize the bellows 52a and 52b. On the other hand, with the leaves in their central position, should the upper leaf 93 be rotated clockwise to apply increased vacuum to the bellows 52a and air to the bellows 52b, a corresponding clockwise rotation of the center leaf 61 will shut off the passage of excess vacuum to the bellows 52a and air to the bellows 52b, and the two bellows will quickly become neutralized.

Referring again to Fig. 2,. it will be seen that integral with the upper leaf 99 is the horizontal extension 99 which is pivotally connected by means of the stud 9'! to the ball joint 98 affixed upon the forward end of the link 99. Affixed upon the link 99 is the stop I99 against which the forward end of the spring I9! compresses.

Referring now to Fig. 2D, it will be seen that the rear end of spring I9I presses against the Washer I92 encircling link 99. Integral with the link 99 is the enlarged portion I93 and encircling this enlarged portion is the sliding sleeve I94. A second washer I95 encircles link 99 and the fore end of a second spring I99 bears against washer I95. Stop I91 affixed upon link 99 positions the rear end of spring 596. Referring now to Fig. 2, it will be seen that the common bellows member 59 is attached to the sliding sleeve I94 so that the sleeve moves with member 56.

Assuming that the elevator centering valve is in the neutral position, in view of the preceding discussion it will be appreciated that the common bellows member 55 will also be in its neutral position. Consequently the bellows 52a, and 5212 will be neutralized. Now assuming that the student in the trainer desires to place the fuselage in a diving position, he will push the wheel 39 toward the head of the fuselage. The vertical members 39 will pivot about the rod 99, the upper ends of these members moving in the same direction as the wheel, and the upper end of the common bellows member 56 will also move toward the head of the fuselage. Sleeve I94 moves in the same direction compressing spring ml and the compression of this spring acting upon the stop I99 moves the link 99 in the same direction. The upper valve leaf 99 will be rotated clockwise as seen from above and according to the previously explained operation of this valve, excess vacuum will be admitted to the bellows 52a and atmosphere will be simultaneously admitted to the bellows 52b. This admission of excess vacuum and air to these two bellows occurs as soon as the wheel 39 is pushed ahead of its neutral position. It will be appreciated that the admission of vacuum into the bellows 52a will tend to collapse the bellows 52a and the air admitted to bellows 52b will tend to expand the bellows 5222. Consequently a force resisting the forward movement of the wheel 39 will be immediately present. This closely simulates the loading placed upon the wheel of a plane in actual flight when the wheel is moved ahead of its neutral position.

When the wheel 39 is in its neutral fore and aft position, the valve 63 is in its neutral position. Should the wheel 39 then be moved by the student to the rear of the neutral position, the upper leaf 69 is rotated in the counterclockwise direction. Simultaneously, excess vacuum is applied to the forward bellows 52b and atmosphere to the rear bellows 52a. Thus a force is immediately present to resist the movement of the wheel 39 rearward from its neutral position, just as in the case of a plane in actual flight.

Assuming that with the wheel 39 and valve 93 in their neutral positions, the student pulls back on the wheel 39, excess vacuum is admitted to the forward bellows 52b and atmosphere to the rear bellows 52a. If then the student merely releases the wheel 39, the vacuum in the bellows 52b and atmosphere in the bellows 52a will move the common center member 56 toward the head of the trainer. The moving of the member 56 in this direction moves the wheel 39 ahead to its neutral position and simultaneously rotates the leaf 68 back to its neutral position. When the leaf 68 reaches its neutral position, the bellows 52a and 52b become quickly neutralized, and the wheel 39, member 56 and leaf 68 remain in their neutral positions. On the other hand should the student push the wheel 39 ahead of its neutral position, excess vacuum is admitted to bellows 52a and air to bellows 52b. If then the student releases the wheel 39, the bellows 52a and 52b move the member 59 and wheel 39 to the rear. The movement of member 59 simultaneously rotates leaf 68 to its neutral position, and when it reaches this position, the bellows 52a and 52b quickly become neutralized, and the wheel 39, member 56 and leaf 99 will be retained in their respective neutral positions.

In view of the foregoing disclosure the conclusion may be drawn that this invention discloses novel means whereby the control Wheel 39 may have a force applied thereto tending to resist movement of the wheel in either direction from its neutral position. Also, when the wheel is moved from its neutral position and released, the wheel will return to its neutral position. Those skilled in the art of flying will appreciate that the bellows 52a and 5212 act upon the control wheel 39 in the same manner that the slip stream of a plane in actual flight acts upon the wheel in the plane through its effect upon the elevator of the plane, to which the control wheel is connected.

It will be appreciated by those skilled in the art of flying and in the field of aviation trainers that as soon as the student moves the wheel 39 to the rear of its neutral position, the fuselage I2 should assume a climbin position and that when the student moves the wheel 39 ahead of its neutral position, the fuselage should assume a diving attitude. This response is obtained simultaneously with the loading of the wheel as described above by means of a part of the apparatus shown in Fig. 2. In that figure it will be seen that the link I I9 is pivotally attached to the right vertical member 38 and the rear end of link or arm I I9 is pivotally attached to the upper end of the lever III. Lever I I I is pivotally connected to the rotor of the shock absorber I I2 which is fixedly mounted upon the upstanding members 48 integral with the bracket 42. To the lower end of the lever III is pivotally connected the forward end of the link II3, the rear end of which is pivotally connected 9 to the arm II lwhich is afiixedto the'upper'lea'f of, the .elevaitorwalve "designated '5. The "con- 'struction'an-d operation "of the elevator valve 1| I -is"well known to the prior art,'it being deemed sufiicient for the purposeof this application to 'statethat the central'stem 5a of this valve'is connected to the manifold designated generally =I'I'I4a whichis positioned as seen in-Fig. 1. vThe manifold is connectedthrough vacuumline I'I lb with the turbine 8.4-so as to'be supplied at all times with a constantlevel of vacuum, as is'well knowninithe priorart. "The ports H5b vand'I I50 of valve H5 are each connected to one of'the pitching bellows I! or .18. Upon a rearward movement ofthe control whee1'30 the upper leaf .of theelevator .valve H5 is moved clockwise and vacuum is admitted to the .rear elevator bellows J3 .and simultaneously therewith atmosphere is admitted .to theforward elevator bellows I'I. On

ltherother-hand whenrthe Wheel 30 ispushed ahead .of its .neutral jposition'lay means of the just described mechanism, vacuumis admitted to the forward pitchingbellows I! and atmosphere to the rearward pitching .hellows I8 thus resulting in ca diving .of the fuselage I2. The position .of the elevator valve 115 depends-at all times upon .the .fore andaft ,pos'itionpf .the wheel 30, and therefore the climbing and diving position of the fuselage I2.depends upon the foreand aft position ofthe wheel, j.ust as the climbing and diving position of a planein actual iflight depends upon the fore and aft :position oflthe wheel.

Thus-the conclusion maybefdrawn that as soon as the studentin the fuselage moves thelcontrol wheel'tll ahead or tolthe rearofits neutral position, the fuselage assumes the ,proper diving or climbing attitudaand that. a force is present to resistthe movemeritofthe control wheel from its neutral position,both of which responses occur in the caseof aplanein actual Jflig'ht. Now assuming that the student in the fuselage has movedthe wheel 3!] from .its neutralposition, vacuum will'be admitteditoone of the bellows 52 or52b.and.atmosphere .tothe other and the-upper leaf .of the elevator valve-will Joe properly turned so that thefuselage will'assumethecorrect pitching (climbing or diving) attitude. Then 'if 'the student'merely releases the wheel 39,the bellows 52a and'52b will returnthe wheel-30to itsneutral position 'and'at the" a i e time the upper leaf of the :elevator valve will also be returned to its neutral position. Simultaneously the upper leaf es of the elevator centering "valve'i53 will'be returned 'to its neutral position. Consequently the fuselage will-assume the level "flight; position, the wheel'will' be returned toits neutral position andthe loading upon -the'wheel will disappear. This closely simul'ates the three responses which occur when the pilot of a plane in "actual flight, having moved the wheel from its neutral position, merely'releases the wheel. The shock absorber 'I I2 dampens the-return of the control 001- uninto its-neutral position underthe'influence oi bellows 52.

"Those skilledin the artof flying will appreciate that the load which-is'placed upon the control wheel'as it .is moved 'iore and aft of i-tssneutral position increases tliefarther-the wheel is moved from the neutral :position. Furthermore, this lead increases with an increase in the :air speed of the plane. This application also discloses means for simulating these tWo factors which afiecttheload upon'the wheel of'a plane inactual night: as the wheel 5 is moved irom its" neutral position.

Cal

Referring again to Fig. 2, .it will be seen that the rear end of the link H6 is .pivotally connected .to theright upstanding member .38 and the forward end of this link is pivotally connected to the lower end of the lever II! which is pivotally mounted upon the stud ;I Ila-held by bracket "II. To the upper end of lever H7 is pivotally connected the link M8, the fore end of which is-pivotally attachedxto the upper end ,of the'arm I I9 which, as bestseen in Fig.'2E, has its lower endpivotall attached to the plate "10 by 'means of stud I20. A stud I2! is integral withthe arm lIQand a slide I22 has two slots 'lfiiltherein. The studs 52! and 25 pass through the "slots I23 inmember I22. Anotherstud I24 is fixedly carried by the upper end of the slide I22 and carried by this stud is the cam roller I25. 'A'cam I26 is pivotally carried by the stud 120 and a spring IZ'I has its upper end attached to the lower'end of slide I22, the-lower endof'spring T2? being attached to the extension 'lla afiixed upon the upper movableportion It of thebellows'l l.

When the wheel at and the centering valve'fi3 are both in the neutral "position, the cam roller 'l il 'l isccntered withrespect to the cam I and thereforea minimum of tension is exerted upon the spring lEl. Consequently the vacuumpresent within the bellows M is at a minimum, e. 'g., o-neinch. As soon as the-wheel 3c is moved'from its neutral position, not only is the upper leaf 8 3 of'the centering valve 63 rotated so as to'cause the'b-ellows Maand 52b to exert a'force pon the Wheel 30 resisting the movement of the wheel from its neutral position, but simultaneously therewith the link I I6 willbe moved and through the operation-of the lever l-I'I and link I IS the upper end of arm H9 will simultaneously be moved. Ihe movement of the arm ll9will, by means of stud IZI, cause arotation of the slide I22 about-an axis through the stud I28. Inasmuchas'the 'cam I26 remains stationary, roller 425 will move out of the central'n-eutral position with-respect'to cam I26, i. e.,'roller 5'25 will move to the left orright and simultaneously the cam IZt-will force this roller-upward, increasing the' tension-upon spring! 2?. The increased tension upon the spring l2! will result in a-greater vacuum within the bellows M, and consequently more vacuum will be applied to the centering valve '63. 'Thus more vacuum will be applied to thebellows 52a or'52b as the wheel '30'is moved farther from itsneutra1 position. The applicationof increased vacuum to the bellows 52am 5% will, of course, result-in an increase in the force resisting themovement of I the control wheel 31] away from its-neutral position. Consequently the greater-the distance the control wheel 30 is moved from its neutral positionythe greater will become Ithe "force opposing further movement of 7 fuselage the greater'is the vacuum within the air speed regulatorbellowsBZ. The greater the vacuum within the bellows 82, the greater will be the vacuumwithin the bellows M and consequently the greater will be the vacuum applied W to the bellows 52a or52b upona movement of the control wheel from its neutral position. Consequently the force resisting a movement of the control wheel 30 from its neutral position is dependent upon the vacuum within bellows 82 which in turn is dependent upon the assumed air speed of the fuselage.

The elevator trimming means which may form a part of my invention will now be described. Referring to Fig. 2, it will be seen that the manually rotatable elevator trimming member I30 is provided, this member being affixed within the fuselage for rotation about the horizontal axis I3I. By means of a right angle drive I32 the screw I33 may be rotated in response to a rotation of the control I30. Rotation of the screw I33 results in an axial movement of the nut I34 and. a corresponding movement of the link I35, the rear end of which is attached to the nut I34 as shown. Movement of the link I35 results in a movement of the arms of bell crank I36 as well as in a movement of the link I31, the rear end of which is pivotally connected to the integral extension 61a of the center leaf 61 of the elevator centering valve 63.

Assuming that the student in the trainer finds that he must exert a constant fore or aft pressure upon the control wheel 30 in order to keep the fuselage in the desired climbing or diving position, it will be appreciated that simultaneously with the holding of the control wheel in the necessary position he will have displaced the upper leaf 68 of the elevator centering valve 63 a given distance from its neutral position. Instead of manually holding the control wheel 30 in the necessary off-center position to maintain the desired attitude of the fuselage, the student may hold the wheel 30 as required and simultaneously rotate the elevator trimming control I30 in the correct direction until the center leaf 61 of valve 63 again assumes a neutral position with respect to the upper leaf 68. In order to accomplish this result it will be appreciated that the center leaf 61 must be rotated in the same direction and through the same angle that the leaf 68 was rotated by the manual holding of the control wheel 30 from its neutral position. When the center leaf 61 has been rotated through this angle, it will be appreciated that it will prevent the application of excess vacuum and atmosphere to the bellows 52a and 52b. The excess vacuum in the bellows 52a or 52b is quickly dissipated as soon as this neutral position is reached and the pressure upon the control wheel 30 is relieved. The control wheel remains in the same position in which it was held in by the student while he was rotating the trim control I30, and consequently the fuselage I2 remains in the same climbing, diving or level flight position. Specifically, it may be stated that if the student finds that he must exert a constant back pressure upon the wheel 30 to maintain the fuselage in the desired pitching position, wheel I30 is rotated counterclockwise, nut I 34 travels ahead, and the center leaf 61a is rotated counterclockwise until the trimmed position is reached. If the student must exert a constant forward pressure, wheel I30 is rotated clockwise to the correct trimmed position.

Accordingly with the apparatus disclosed in Fig. 2 the student in the trainer may trim the fuselage so that he does not have to exert a constant pressure upon the control wheel 30 in order to keep the fuselage in the desired pitching attitude. It will be appreciated that this trimming of the trainer may be used by the student to climb or dive the trainer at a given angle or to fly the train-er at a constant altitude.

It will be appreciated by those skilled in the art of flying that the trimming of one of the control surfaces to relieve the pressure upon the control associated with that surface establishes a new position for the control at which no pressure is present upon the control. As the control is then moved from this new position, a load is immediately placed upon the control, and the farther the control is moved from the trim-established zero pressure point, the greater becomes the pressure. If the control is released, the control surface and the control connected thereto return to the trim-established zero pressure point and not to the absolute neutral positions. The following means incorporated herein simulate this functioning of the control surfaces and controls of actual aircraft, as far as the elevator and fore and aft position of the wheel are concerned.

Referring to Fig. 2 it will be appreciated that as the nut I34 moves axially of the screw I33, the link M0 moves therewith. The bell crank MI is turned and the transverse link I42 is moved resulting in a movement of the bell crank I43 and rearwardly extending link I44. The rear end of link I 44 is pivotally attached to the lower end of the cam I26 through the universal connector 544a, and, consequently, the cam I26 moves whenever the elevator trimming control I30 is rotated. The movement of cam I26 will change the vertical position of roller I25 and consequently the tension upon spring I21.

Let us assume that the student must place the wheel 30 in a position to the rear of its neutral position in order to maintain the fuselage in the desired climbing attitude. In movin the wheel 36 from its neutral position it has been explained that the upper leaf of the valve 63 is rotated so as to admit vacuum to the bellows 52b and atmosphere to the bellows 52a. The elevator valve H5 is operated to place the trainer in the desired climbing attitude and the movement to the rear of the wheel 30 simultaneously results in a movement toward the head of the trainer of the cam roller I25. The roller I25 is raised and the tension upon spring I21 is increased-the farther the backward movement of wheel 30 the greater the relative motion between the roller I25 and the cam I26. Then, when the student rotates the elevator trim control I30 counterclockwise in order to move the leaf 61 of valve 63 to relieve the pressure upon the wheel 30, the link I54 simultaneously moves toward the rear of the trainer and the cam I26 rotates clockwise about the pivot I20. This rotation of the cam I26 allows spring I21 to pull the slide I22 and roller I25 downwardly, and when the leaf 61 is positioned by the student in the neutral position with respect to the leaf 68, the roller I25 is in the lowermost position with respect to cam I26. Thus the trimming of the trainer relaxes the tension which is placed upon the spring I21 when the wheel 30 is moved away from its neutral position so that when the elevator is properly trimmed, a normal or neutral tension is placed upon spring I21. As previously explained, the wheel 30 will remain displaced from its absolute neutral position and in the position in which the student had to hold the wheel to maintain the fuselage in the desired climbing position. Consequently, thereafter, should the student desire to move the wheel 30 farther to the rear, the pressure which he must exert upon the wheel is decreased by the amount that he removed when he .the movement of the elevator.

'had zpreviously trimmed the trainer. Thus the trimming of the elevator by the student estabalishes a new neutral pressure point just as is the casein actual flight.

It'will be appreciated that if the student finds he must hold the wheel forward to maintain the fuselage in the desireddiving position, when he trims the fuselage he will establish a new zero pressure point.

In the flight of .actual aircraft equipped with elevator trimming means, the climbing and diving-position of the plane may be-controlled by a manipulation of the elevator trimming control. Thus, when it is desired to lower the nose-of the plane the trim tab'control may be rotated in the proper-direction resulting in a movement of the elevator so that the nose drops. As the elevator .moves, thecontrol wheel-moves to the fore. On

the other hand, when it is desired to raise the nose of the plane, the trim control may be m .tated in the opposite direction, the elevator moves in the opposite direction, and-the nose of the plane rises. The wheel moves to the rear with The previously disclosed simulated elevator trimming means of this invention may also be used to simulate this sometimes used method of controlling the climbing or diving attitude of a plane in actual flight.

Referring to Fig. 2, assuming that the wheel 30 and leaves of valve 63 are centered, if the student rotates the control I30 clockwise, the center leaf E1 of valve-63 is rotated clockwiseadmitting'vacuumto the bellows 52b and air to the bellows 52a. The central bellows member 5% moves ahead, carrying with it the wheel 38, and the elevator valve H5 is operated to place the fuselage in a diving position. The forward movement of the member 56 simultaneously causes a clockwise rotation of the leaf 68 of valve 63. Bellows 5212 will be collapsed, moving member 56 ahead and rotating leaf 68 clockwise until this leaf is-again neutrally positioned with'respect to the leaf 61. When this position is reached the member 55 is stopped, the pressures within bellows 52a and 52 become neutralized, and the wheel 30 is held ahead of its neutral position at a point depending upon angular movement'of the simulated elevator trim control I30. The nose of the fuselage will be lowered as a result of the rotationof the upper leaf of the elevator valve An opposite rotation of thesimulated'elevator .trim control I 39 will produce reversed movements of the same. parts of the apparatus just considered.

In View of the detailed disclosure of the preferred embodiment of my simulatedelevator trimming means for use in grounded aviation trainers, it will be understood that I have provided-apparatuswhich accomplishes the following results:

:1. In the neutral'position there is no load upon the control wheel, but as the wheel is moved ahead-or to the'rear of the neutral position, a load is immediately placed upon the wheel to resist themovementof the wheel and this load increases .thefarther the wheelismoved from its neutral position. The fuselage, simultaneously with a movement of the wheel from its neutral position, assumes the proper climbing or diving attitude.

2. When the wheel is moved from its neutral position the load placed upon the wheel is dependent upon the. assumed air speed of the trainerthe higher the assumed air speed the greater the load.

3. .The student may use theprovided simulated elevator trimming means to relieve the :pressure from the control zwheel when he-finds that he ;moved from the-x wheel, just (as he would do in actual flight. When lthis point is reached the simulated elevator trimming means are properly positioned and the wheel is notmoved as a result of the movement of the trimming means. The operation of the simulated elevator trimming means establishes a-new neutral point insofar as pressure upon the wheel is concerned.

4. Alternatively, the simulated elevator trimming control may be used by the student to change the pitching attitude'of the fuselage, just as the elevator trimming control in a real plane maybe usedto change. the pitching attitude of the plane. When-this method-of'operation is used the 'fore and aftposition of the wheelas well as :the position of the upperleaf of the elevator valve changes with the rotation of the simulated trimming control.

Simulated aileron loading and trimming means Reference is now.made to Fig. 3 which discloses .in-detail the preferred embodiment of the simulated aileron loading and trimming means which mayform a part of myinvention. In Fig. 3 the wheel 39 andmainshaft 32 upon which the wheel is affixed are shown. A bracket I69 is fixedly attached to the interior .of .the fuselage I2 some distance above the floorthereof and the bracket It I .is fixedly attached to the bracket Hill. A plurality of upstanding members I62 integral with. bracket I5 Isupport the aileron-control loading bellows assembly designated generally by I63. This bellows assembly, for all practical purposes, is identical with the elevator control loading bellows assemblyshown in Fig.2. A pair of side plates IMare provided, theseplatesholding in a fixed position the end members E65 of the two bellows of the assembly. A common central member B66 is provided to form two independent bellows, the left bellows being designated I631; and the right bellows beingdesignated I631). The vacuum-air line I6'I connects bellows I63a with the aileron centering valve designated generally by I68 while the vacuum-airline I69 connects the bellows 53b with the valve I68. The aileron centering valve I68 is of identical construction as'the elevator centering valve'63 shown in detail in Fig. 23.

Still referringto Fig. 3, it will be seen that there is afiixed on the shaft '32 a gear I10 meshing with the sector Ill. The arm H2 is integral with sector ill and the lower end of link I13 is pivotally connected tothe outer end of arm I12. The upper end of link I13 is pivotally connected to the rear arm of bellcrank I'M, this bellcrank being pivotallymounted on the transverse shaft H5 held by the brackets I'IG which in turn are held by the rigid side plates I64. To the upper end of bellcrank I I4 is pivotally attached the rear end oflink I17, the fore end-of which is pivotally connected-to the top of the common bellows forming member 166. Link I18 is provided, this link having itsfore end attached to the common bellows member I66 through a compensating. spring arrangement designated generally by I79, this spring arrangementibeingidentical with-that disclosed in Fig. 2D. The rear end of the link I18 is connected to the upper rotatable leaf I80 of the valve I68.

The central stem of the aileron centering valve I68 is connected through the vacuum line I8I to the aileron control loading regulator bellows des ignated generally :by I92. This bellows is constructed the same as the bellows shown in Fig. 2C and is connected through the vacuum line I83 to the airspeed regulator bellows designated generally by 82. As shown in Fig. 2, bellows 82 is connected to the turbine 84.

In view of the marked similarity of the construction shown in Fig. 3 to that previously described connection with Fig. 2, it should be understood that when the wheel 39 is in its neutral rotational position (to be distinguished from the neutral fore and aft position), the upper rotatable leaf I96 of the aileron centering valve 568 is in its neutral position. When the middle leaf I84 of this valve is also centered, the bellows I630: and [69b have equal pressure therein and consequently there is no load upon the wheel 30. However, assuming that the student in the trainer turns the wheel counterclockwise as he would do to bank the fuselage to the left, through the gear I'lll, gear sector Ill and arm H2, link lit, bellcrank I'M and link II'I, the upper end of the common bellows member I66 would be pushed ahead, member I66 pivoting about the axis I65. This movement of member I66 results in a movement to the head of the fuselage of link H8 and the upper leaf 189 of the aileron centering valve I68 is rotated counterclockwise. Immediately, in-

creased vacuum is applied to the interior of the bellows I63?) and air to the interior of the bellows I93a. Consequently, a force is instantly present upon movement of the wheel 39 from its neutral position tending to resist such movement of the wheel.

On the other hand, should the wheel 39 be moved clockwise of its neutral position it will be appreciated that the direction of rotation of the leaf I89 will be reversed and increased vacuum will be applied to the interior of the bellows I634: while atmosphere will be applied to the interior of the bellows I631). Similarly, as soon as the wheel is moved clockwise of its neutral position the bellows i69a and I632) operate to exert a force resisting the movement of the wheel 39.

If the wheel 39 is rotated from its neutral position it will be appreciated that if the student merely releases the wheel the bellows I630. and 5631; will return it to its neutral position. A shock absorber i'iia having afiixed upon its rotor the arm Illb is provided, arm IlIb being actuated by stud IlIc affixed to the lower extension Illd of sector Hi. This shock absorber dampens the return of wheel 39 to its neutral position under the influence of the bellows I63.

As soon as the wheel is moved from its central or neutral position, the fuselage should, of course, bank to the left or right, the direction of bank depending upon the direction of rotation of the wheel 39 from its neutral position. This response is also accomplished by the apparatus shown in Fig. 3. Affixed to the sector Ill for rotation therewith is the rearwardly extending shaft I99 upon the rear end of which is affixed the arm I69. The upper end of link I99 is pivotally connected to the outer end of arm I89, and as seen in the upper right portion of Fig. 3, to the lower end of the vertical link I99 is pivotally attached the left end of arm I9I. The other end of arm I9I is affixed to the fore end of shaft I92 which runs rearwardly to the arm I93, the lower end of which is affixed upon shaft I92. To the upper end of arm I93 is pivotally connected the left end of link I94, the right end of which is pivotally connected to the upper leaf I95 of the aileron valve designated generally by I96. The position of the aileron valve I96 in the trainer fuselage is shown in Fig. l.

The aileron valve I96 is of the conventional well-known construction, for our purposes it being sufficient to know that the central stem of this valve is connected to the manifold IMa which is connected to the turbine 84 through the vacuum line H412, seen in Fig. 1. Valve I96 is connected to the left and right banking bellows I9 and 29 shown in Fig. 1, by means of lines I961) and I960. Upon a counterclockwise rotation of the upper leaf I95 in one direction, vacuum is admitted to the left banking bellows and atmosphere to the right banking bellows, the left bellows collapsing and the right bellows expanding to cause a banking of the fuselage to the left. A rotation of the leaf I95 in the opposite direction admits vacuum to the right banking bellows and air to the left banking bellows and the trainer banks to the right.

Assuming that the control wheel 39 is in the neutral position and that the leaves of the main aileron valve I96 are similarly positioned, when the student in the trainer rotates the wheel 30 counterclockwise of its neutral position, the bellows I63a and 5631) not only instantly exert a force tending to resist the rotation of the control wheel but simultaneously therewith the upper leaf I95 of the aileron valve I96 is rotated counterclockwise and the trainer banks to the left. On the other hand, should the wheel 30 be rotated clockwise of its neutral position, the bellows 463a and I631) similarly exert a force tending to resist the movement of the control wheel and simultaneously therewith the upper leaf I95 of the aileron valve I 96 is rotated clockwise and the trainer banks to the right.

As is well known to the prior art, the degree of bank of the fuselage will depend upon the extent of the movement of the wheel 30 from its neutral position.

It will therefore be appreciated that this invention also discloses means whereby upon a movement of the control wheel from its neutral position, a force will be exerted which will tend to oppose the movement of the control wheel, thereby simulating the resistance to the movement of the control wheel in a plane in actual flight as a result of the slipstream acting upon the ailerons. At the same time as the wheel is moved from its central position, the fuselage I2 is properly banked.

As explained above in connection with the simulated elevator system of this invention, in the case of actual aircraft as the wheel is moved fore and aft to operate the elevators of the plane the resistance to movement of the wheel caused by the slipstream increase the farther the control wheel is moved from the neutral position. The same is true in actual aircraft as far as movement of the ailerons and aileron control is concerned. The following means may form a part of this invention to simulate this phenomenon of actual flight.

Referring to Fig. 3, it will be seen that the fore end of the link 209 is pivotally connected to the central bellows member I66 and the rear end of this link is pivotally connected to the lower end of lever 20I which is pivotally mounted on the stud 202 carried by the plate I64. The fore end of link 203 is pivotally connected to the upper end of lever 20I and the rear end of this link is pivotally attached to the upper end of arm 204 which is mounted for rotation upon the stud 205 held by the plate 206 which in turn is held by the plates I16 and 201 aflixed to the main sideplate I64. Referring to Fig. 3A, the stud 201a is carried by arm 204 and passes through a slot 208 in the slide 200. A second lot H is in the slide 209, stud 205 passing through the slot 2I0'. Affixed to the lower end of slide 200 is the spring 2| I, the lower end of which is affixed to the upper movable portion 2l2 of the aileron control loading regulator bellows I82. This bellows is also carried by the plate 206. The cam 2I3 is pivotally mounted upon the stud 205 and the upper end of slide 209 carries a stud 2 I4 upon the outer end of which is rotatably mounted the roller 2I5, roller 2l5 engaging the surface of cam 2I3.

It will be appreciated that an arrangement similar to the one just described has been disclosed in connection with the simulated elevator system.

Assuming that the control wheel 30 and the leaves of the aileron centering valve I68 are in their respective neutral rotational positions, the

roller 2 I5 i in its lowermost position with respect to cam 2I3, Then assuming that the student moves the control wheel 30 counterclockwise of its neutral position, the fuselage banks through the operation of the aileron valve I96 and simultaneously therewith the link II'I moves the central bellows member I66 ahead. Link I18 moves ahead and the upper leaf I80 of the aileron centering valve I68 is rotated counterclockwise as seen from above, admitting increased vacuum to the bellows I631) and atmosphere to the bellows I63a, thus producing a force opposing the movement of the wheel 30. Simultaneous with the movement of the bellows member I66, the link 200 moves ahead and the link 203 moves to the rear. The arm 209 rotates clockwise about the stud 205 and by means of the stud 201a, the slide 209 is rotated in the same direction about the stud 205. Inasmuch as cam 2I3 remains stationary, roller 2I5 is moved upward by its coaction with cam 2I3 and the tension upon spring 2 is increased. Consequently, the vacuum within the regulator bellows I82 increases and a greater amount of vacuum is applied through the centering valve I68 to the bellows I631). The farther the control wheel 30 is moved from its neutral position the greater becomes the vacuum within bellows I631) and consequently the greater becomes the force opposing further movement of the wheel 30. Consequently, as the wheel 30 is moved a greater distance counterclockwise of its neutral position, the greater becomes the vacuum within bellows I631) and the greater is the force opposing the movement of the wheel. This simulates the increasing force tending to resist the counterclockwise rotation of the wheel in actual flight as the wheel is moved farther from its neutral position.

On the other hand, should the wheel 30 be moved clockwise of its neutral position, it will be appreciated that the fuselage assumes a right banking position, increased vacuum is admitted to the bellows I63a and air to the bellows I631). The movement of the central bellows member I66 simultaneous with a rotation of the wheel 30 results in a counterclockwise rotation of the arm 204 about the axis of stud 205. A similar rotation of the slide 209 will occur and the roller H5 will be forced upward by the cam H3. The tension upon spring 2 will increase as will the vacuum within the regulator bellows 2I2. Consequently, the Vacuum within bellows I63a will increase the farther the wheel 30 is moved from its neutral position and thus with increased rotation of the wheel 30 a proportionately greater force is exerted tending to resist the movement of the wheel.

Referring again to the procedures of actual flight for purposes of comparison, .if the pilot in the plane finds that he must constantly hold the wheel in a given rotational position in order to keep the plane in the desired banking position he may, if his plane be so equipped, trim the ailerons to relieve the pressure upon the wheel. When this has been done the plane will fly in the desired banking position,

This phase of actual flight may be simulated by the following means which are disclosed by this application. Referring to Fig. 3, the aileron trimming control which is manually operated is designated by 220 and is aflixed upon the rear end of the horizontal shaft 22I, upon the fore end of which is affixed the gear 222. Gear 222 meshes with the gear 223 which is afiixed upon the lower end of the flexible shaft 224 inside the conventional flexible shaft sheathing 224a. Referring to the upper center portion of Fig. 3, the continuation of flexible shaft 224 is shown and this flexible shaft drives the screw 225 rotatably mounted in the bracket 226 which is carried by the plate 206. A nut 22'! is mounted upon the screw 225, this nut carrying the stud 228 which engages the left end of the rod 229. The other end of rod 229 is connected to the integral extension 34a. of the middle leaf I84 of the aileron centering valve I68.

In view of the just described arrangement, if

the student finds that the wheel 30 must be held in a given counterclockwise rotational position in order to place the trainer in the proper banking position, it will be appreciated that in so holding the wheel he will have moved the upper leaf I of the centering valve I68 to a given position counterclockwise of its neutral position. This position of the upper leaf I80 will have admitted increased vacuum to the bellows I631) and air to the bellows l63a so that a force must be constantly exerted upon the wheel 30 to hold it in the necessary position. The student may then by a counterclockwise rotation of the simulated aileron trim control 220 and the described intermediate connections move the nut 22! to the right along screw 225. In so moving the nut 22'! the center leaf I84 of the centering valve I68 is rotated counterclockwise. When the leaf I84 has been rotated counterclockwise of its neutral position through the same angle as the leaf I80 was rotated by the clockwise rotation of wheel 30, the leaves I80 and I84 are neutrally positioned with respect to one another and the same amount of vacuum leaks through the valve I68 into the bellows I63a and I631). The pressure within the bellows I63a and I631) is rapidly equalized and the central bellows member I66 remains in the position in which it was placed by the original counterclockwise rotation of the control wheel 30. Accordingly, the force exerted by the bellows I63a and I631) upon the central member I66 disappears and the force tending to rotate the wheel 30 clockwise simultaneously disappears. The wheel 30 remains in the position in which it was held by the student before he regulated the simulated aileron trim control 220. and the banking position of the fuselage remains unchanged.

It will be understood without a detailed explanation that should the student find that he must hold the wheel 30 in a given. position clockwise from its neutral position in order to maintain the fuselage in the desired position about its longitudinal axis, a clockwise rotation of the simulated aileron trim control 220 throughthe correct angle will properly position the center leaf I84 of the centering valve I681 relative to the top leaf I80 so that the force exerted by the bellows I 63a and I632) tending to rotate the wheel 30 counterclockwise will disappear, leaving the wheel 30 in the position in which it was being held by the student. Accordingly the pressure is removed from the wheel and. the fuselage maintains the banking position in which it was placed by the student holding the control wheel before he manipulated the simulated aileron trim control 220.

Accordingly it will be appreciated that this invention discloses means whereby when the student finds that he must hold the control wheel 30 in a given rotational position in order to maintain the fuselage in the correct banking position, he may, by means of the simulated aileron trim control, relieve the pressure from the wheel just as he would do in actual flight.

It was explained in connection with the simulated elevator trimming means of this application that in actual flight the trimming of the elevators of the plane establishes a new zero point insofar as pressure upon the wheel caused by the slipstream is concerned. The same is true when the ailerons of a real plane in actual flight are trimmed and the following means may form a part of this invention in order to simulate this effect of the trimming of the ailerons of a plane in actual flight. Referring to Fig. 3 it will be seen that the stud 230 is affixed to the nut 22'! for movement therewith and that the lower end of this stud engages the right end of the link 23I, the left end of which is pivotally attached to the rear end of the upper arm 232 of the bell crank designated generally 233. Bell crank 233 is held by the bracket 234 afiixed to the stationary plate 206. The lower member of the bell crank 233 is designated 235 and to this lower arm is pivotally attached the rear end of link 236, the fore end of which is pivotally connected to the lower end of cam 2 I3.

It has been explained that when the student rotates the wheel 30 from its neutral position, the farther the wheel is rotated the increasing rotation of the slide 209 results in an upward movement of the roller 2I-5 because of the presence of cam 2I3. Consequently the greater the distance wheel 30 is rotated from its neutral position, the greater becomes the tension upon spring 2 and the resultant increase in vacuum within the regulator bellows I82 results in a greater force acting upon the central bellows member I66. Assuming that the student finds that he must hold the wheel 30 in a given counterclockwise position from its neutral point, it has been explained that the central bellows member I66 will be moved ahead of its neutral position. Link 200 similarly will be moved ahead of its neutral position and link 203 will be moved to the rear. The arm 204 will be rotated clockwise from its neutral position and the roller 2I5 will be moved to the rear of the center of cam 2I3. Then, assuming that the student desires to use the simulated aileron trimming control 220 to remove the pressure upon the wheel 30, he will rotate the control knob 220 counterclockwise and the nut 22'! moves to the right, link 23I will move in the same direction and by means of the bell crank 233, link 236 will move ahead of its neutral position. Consequently the cam 2I3 will be rotated clockwise and when the center leaf I84 of the centering valve I68 is neutralized with respect to the upper leaf I80, the cam 2 I3 will be positioned such that the roller 2I5 is in the center of this cam. Consequently roller 2 l5 will be in its lowermost position and the tension upon spring 2 will be relaXed to a minimum. Consequently, if the student thereafter desires to manually move the control wheel 36 from the trimmed position, the load which will be instantly placed upon the wheel will not be dependent upon the position of the wheel with respect to the absolute zero position, but will be dependent upon the position of the wheel from the new neutral position established by the trimming of the simulated'aileron control. This simulates the establishing of the new zero pressure point when the ailerons of a plane in actual flight are trimmed. It will be appreciated that a new zero pressure point is also established when the simulated aileron trim control 220 is rotated counterclockwise to obviate the necessity of the students holding the wheel in a given clockwise position from its neutral point in order to maintain the fuselage in the desired banking position.

Without a detailed explanation it should be understood that with the wheel 30 and simulated aileron trim control 220 positioned so that no pressure is upon the wheel, a clockwise rotation of the simulated aileron trim control 220 will result in a clockwise rotation of the wheel 30 and a banking of the fuselage to the left. On the other hand, a counterclockwise rotation of the control 220 will, under the same circumstances, result in a counterclockwise rotation of the wheel 30 and a banking of the fuselage to the right. These rotations of the wheel 30 in response to a rotation of the control 220 occur because the valve I68, responsive to the control 220, operates the bellows I63a and I63?) which then moves the wheel 30 through the intermediate connecting members.

Insofar as the simulated aileron control trimming means disclosed by this invention is concerned, it will be appreciated that the similarity in structure produces the same novel results as explained in detail toward the end of the discussion of the simulated elevator trimming means.

Simulated rudder loading and trimming means Reference is now made to Fig. 4 which discloses in detail the simulated rudder loading and trim ming means of this application. In Fig. 4 it will be seen that there is provided a pair of brackets 250, these brackets being aflixed to the inside of the fuselage a substantial distance above the floor at a point ahead of the students seat, as seen in Fig. 1. A pair of rods 25I are held by the brackets 250, and pivotally carried by each of the rods is a ratchet member 253. Also pivotally carried by each of the rods 25I is a depending U-shaped bracket 254 having rotatably mounted in the lower portion thereof a transverse shaft 255 upon each of which is fixedly mounted one of the rudder pedals 256. Fixedly attached to the inner end of each of the shafts 255 is an arm 25? to the rear end of each of which is pivotally attached a generally upstanding link 253, the upper end of each of which is pivotally attached to its associated bracket 250. An arm 252 is affixed to each of the ratchets 253, as shown, and pivotally attached to the bottom end of each of the arms 252 is a forwardly extending link 259, the forward end of each of which is pivotally connected to one end of the rudder bar 266 which is pivotally mounted upon the stud 26| carried by the bracket 262 which is fixed to the bottom of the fuselage floor. A dog 263 is pivotally carried by each of the U-shaped brackets 254, and it will be appreciated that by selectively positioning the engaging end of each dog with respect to the teeth in the adjoining ratchet 253, the rudder pedals 256 may be positioned according to the individual requirements of the student using the trainer. The springs 264 assure the constant engagement of the dogs and ratchets.

Afixed to the left depending arm 252 is the rear end of the forwardly extending rod 265 which is afiixed to the rear portion 266 of the left rudder control loading bellows designated generally by 261. It will be seen that this bellows comprises a central member 268 and a forward member 269 as well as the suitable covering material 216. A plurality of holes 268a and 2631) are drilled through member 268, as shown.

The rod 211 has an enlarged forward end and is fixed to the forward end 266 of bellows 251. The forward end of this rod is pivotally attached to the lower end of the arm 212 carried by the fixed bracket 256. It should be noted that the rear end of the rod 21I passes through hole 26% in the central member 268 of the bellows 261 and telescopes inside the rod 265.

A rod 214, bellows designated generally 215, rod 216 and arm 211 are provided, these parts being constructed exactly like the corresponding members just described. The left rudder control loading bellows 261 is connected by means of the air-Vacuum line 218 to the rudder centering valve designated generally by 219 and the right rudder control loading bellows 215 is connected by means of the air-vacuum line 286 to centering valve 219. Valve 219 is of identical construction with the elevator centering valve designated generally by 63 in Fig. 2 and shown in detail in Fig. 2B. In Fig. 4 it will be noted that the upper rotatable leaf 281 of valv 219 has attached thereto the rear end of the link 282, the forward end of which is pivotally connected to the rudder bar 266. It will be noted that the central portion of the valve 219 is connected by means of the vacuum line 283 directly to the turbine 84.

Assuming that the rudder pedals 256 are in their neutral positions and that the leaves of the valve 219 are similarly positioned, should the student desire to turn the fuselage to the left he will of course press forward upon the left rudder pedal. The left link 259 moves ahead; the rudder bar 26!] rotates clockwise as seen from above, and simultaneously therewith the right link 259 moves to the rear, thus pushing the right rudder pedal 256 toward the rear of the fuselage. Simultaneously, with the rotation of the rudder bar 260, the link 282 moves ahead and the upper leaf 28I of the valve 219 is moved clockwise. Immediately air is introduced into the bellows 261 through the line 218 and increased vacuum is introduced into the bellows 215 through the line 286. The expansion of the bellows 266 and the contraction of the bellows 215 immediately exert a force tending to oppose the foward movement of the left rudder pedal 256. This opposing force resisting the movement of the rudder pedal 256 simulates the effect upon the slipstream of the rudder of an actual plane when the pliot presses the left rudder pedal forward.

0n the other hand, with the rudder pedals 256 in their neutral position should the student push the right rudder pedal 256 forward, it will be appreciated that the rudder bar 266 will rotate counterclockwise, the link 282 will move to the rear and the upper leaf 28! of valve 219 will be rotated counterclockwise. Instantly, air will be admitted to the interior of bellows 215 and increased vacuum to the interior of bellows 261. Both of the bellows will, therefore, resist the forward movement of the right rudder pedal 256, again simulating the load upon the rudder pedals of a plane in actual flight caused by the slipstream.

A capillary is placed in both of the lines 218 and 286 to prevent a sudden over-application of vacuum to the bellows 261 and 215.

It will be appreciated that whenever the rudder pedals 256 are displaced from their neutral positions, the fuselage [2 should rotate with respect to the stationary base lb-to the left when the left rudder pedal is forward and to the right when the right rudder pedal is forward. In Fig. 4 it will be seen that the fore end of link 3lll is pivotally connected to the rudder bar 266 and that the rear end of this link is similarly connected to the upper rotatable leaf 325 of the main rudder valve 3l2. This rudder valve is of the well-known conventional construction, having its central stem connected to manfold l Ma which in turn is connected through vacuum line H417 to the turbine 66, and its ports 328 and 329 to the turning motor 22. When the left rudder pedal 256 is pressed forward the right rudder pedal simultaneously moves to the rear by an equal amount, as does link 3H1, the upper leaf 325 moves counterclockwise as seen from above, and the turning motor 22 is energized in such a direction that the fuselage 12 rotates to the left. Opposite rudder pedal movements result in opposite movements, the fuselage rotating to the right.

Also, in the case of actual aircraft when one of the rudder pedals is moved forward, the other moves to the rear, and if the pilot removes his foot from the forward pedal the slipstream pres sure upon the rudder centers the rudder, and inasmuch as the rudder pedals are connected to the rudder they also are centered. The apparatus disclosed in Fig. 4 simulates this response of the rudder pedals in actual flight. In the left rudder pedal 256 is forced ahead of its neutral position, air is admitted to the bellows 261 and excess vacuum to the bellows 215. These two bellows thus exert a force upon both of the rudder pedals tending to return them to their neutral positions. Consequently, if the student removes his foot from the left rudder pedal, the bellows will return the rudder pedals toward their neutral positions and when-they reach their neutral positions the upper leaf 26 of valve 216 will be centered, equalizing the pressure within the bellows and thus preventing further movement of the rudder pedals.

Without a detailed explanation it will be understood that should the right rudder pedal be moved forward and the left rudder pedal moved to the rear, when the student releases his foot from the right pedal the bellows will return the pedals and upper leaf 261 to their neutral positions, at which points the rudder pedals remain.

In both cases it will be noted that when the rudder pedals are displaced from their neutral positions the upper leaf 325 of the rudder valve 3I2 will be displaced from its neutral position in the proper direction so that the trainer turns to the left or right. When the rudder pedals are returned to their neutral positions by the bellows, the upper leaf 325 is simultaneously re-- turned to its neutral position and the turning of the fuselage stops.

Under most flying conditions, most planes will not fly perfectly straight with the rudder in the dead center position. If the plane is not equipped with rudder trimming means it is necessary for the pilot to hold the rudder pedals in the correct position in order to keep the plane flying a straight course. Different pressures will have to be applied under different circumstances. For example, on the take-01f it may be necessary to apply a great deal of right rudder in order to keep the plane flying straight down the runway. In cruising, left rudder may be necessary. In order to render it unnecessary for the pilot to apply a given amount of rudder over a long period of time, in order to keep the plane flying the desired course, aircraft of the type being simulated generally are equipped with rudder trimming means whereby the plane may be trimmed in order to keep it flying the desired course without the pilots constantly applying a corrective pressure to the rudder pedals.

Simulated rudder trimming means are also provided by this invention and for a disclosure thereof reference is made to Fig. 4 where the simulated manual rudder trimming control is designated by 299.' Upon a manual rotation of knob 299, the right angle drive 29| causes a rotation of the shaft 292 upon the forward end of which is afiixed the screw 293. A nut 294 coacts with screw 293 to travel longitudinally thereof upon a rotation of the screw, and stud 295 travels with the nut 294. A bracket 296 is aflixed to the interior of the fuselage l2 and the lower end of arm 291 is pivotally mounted upon this bracket. A horizontal extension 298 is integral with arm 291 and pivotally connected to extension 299 is the upper end of the walking beam 299. Walking beam 299 is pivotally mounted on stud 295 as shown. Integral with the lower end of walking beam 299 is the horizontal extension 399, and pivotally mounted upon the right end of this extension is the lower end of arm 39]. A pair of links 302 and 393 are pivotally attached to arm 39! and beam 299 as shown. For present purposes, it is suflicient to know that link 392 is connected to means within the fuselage responsive to changes in the airspeed of the fuselage. Consequently the link 392 always assumes a position dependent upon the assumed airspeed. Link 3934s connected to the simulated throttle lever in the trainer so that it changes in response to a movement of the throttle lever. Insofar as understanding the operation of the simulated rudder trim control of this invention is concerned, the links 392 and 393 may be considered stationary thus providing a fixed pivot for the lower end of the walking beam 299.

Aflixed to the arm 291 is the rear end of link 394, the forward end of which is aflfixed to the upper arm of bellcr'ank 395. The left end of link 306 is pivotally attached to the lower arm of hellcrank 395 and the right end of this link is pivotally attached to the center leaf 391 of the rudder centering valve 219.

Whenever the student in the fuselage finds that he must apply a constant pressure to one of the rudder pedals in order to maintain the fuselage upon the desired heading, it seems clear that the upper leaf 28! of the valve 219 will be displaced from its neutral position and consequently that the bellows 261 and 215 will exert a constant force tending to return the rudder pedals to their neutral positions. The rudder valve 3I2 will be positioned so that the fuselage maintains the desired heading.

Instead of so positioning the rudder pedals by means of his feet, the student may by rotating the simulated rudder trim control 299 move the nut 294 in the desired direction. Movement of this nut results in a pivoting of the walking beam 299 about its lower end and the arm 291 is pivoted about its lower end. Link 394 moves in the correct direction, as does link 396, the center leaf returned to its neutral position. Consequently,

the positions of the rudder pedals 256 are not changed and neither is the relative positions of the leaves of the rudder valve 3|2. Accordingly, the trainer maintains the desired heading.

Specifically, let us assume that the student in order to maintain the fuselage upon the correct heading finds that he must exert a constant pressure upon the left rudder pedal 256. The upper leaf 28l of the control valve 219 will be rotated clockwise a given distance from its neutral position while the upper leaf of the rudder valve 312 will be rotated a given distance counterclockwise from its neutral position. Atmosphere will be admitted to the bellows 261 and vacuum to the bellows 215. The student will then rotate the simulated rudder trim control 290 counterclockwise as seen from above and the nut 294 moves toward the head of the fuselage. The middle leaf 391 of the valve 219 will be rotated clockwise and when this leaf is centered with respect to the upper leaf 28I the pressure within the two bellows 261 and 215 will become quickly neutralized. The position of the rudder pedals 256 and .of the upper leaf of the rudder valve 3l2 will be undisturbed with the releasing of the pressure caused by the bellows upon the rudder pedals.

It should be noted that the load placed upon the simulated rudder pedals, when the pedals are moved from their neutral positions, is independent of the assumed airspeed .of the trainer and of the extent which the pedals are moved from their neutral positions. However, such means may be provided, in view of the above disclosure relating to the aileron and elevator systems, if such means are desired.

It will be appreciated that numerous changes may be made in the preferred embodiment of my invention without departing from the spirit thereof. All such changes are intended to be covered by the following claims. Furthermore, my invention is not necessarily restricted to use in grounded trainers of the type illustrated.

I claim:

1. In a grounded flying training device of the type including a simulated fuselage having a seat for a student, the combination .of a member simulating a flight control member of an actual aircraft positioned near said seat; a pneumatically operated member connected to said flight control simulating member; a control valve connected to said pneumatically operated member for controlling the operation of the same; and a connection between said flight control simulating member and said control valve for operating said control valve upon movement of said flight control simulating member in either direction from a predetermined neutral position for causing said pneumatically operated member to exert through its connection with said flight control simulating member a force upon said flight control simulating member opposite the direction of movement of said flight control simulating member.

2. In a grounded flying training device of the type including a fuselage having a seat for a student, the combination of a member simulating the banking control member of an actual aircraft positioned near said seat; a pneumatically operated member connected to said banking control simulating member; a control valve connected to said pneumatically operated member for controlling the operation of the same; and a connection between said banking control simulating member and said control valve for operating said control valve upon movement of said banking control simulating member in either direction from the predetermined neutral position for causing said pneumatically operated member to exert through its connection with said banking control simulating member a force upon said banking control simulating member opposite the direction .of movement of said flight control simulating member.

3. In a grounded flying training device of the type including a fuselage having a seat for a student, the combination of a member simulating the pitching control member of an actual aircraft positioned near said seat; a pneumatically operated member connected to said pitching control simulating member; a control valve connected to said pneumatically operated member for controlling the operation of the same; and a connection between said pitching control simulating member and said control valve for operating said control valve upon movement of said pitching control simulating member in either direction from the predetermined neutral position for causing said pneumatically operated member to exert through its connection with said pitching control simulating member a force upon said pitching control simulating member opposite the direction of movement of said flight control simulating member.

4. In a grounded flying training device of the type including a fuselage having a seat for a student, the combination of a pair of simulated rudder pedals positioned near said seat; pneumatically operated means connected to said simulated rudder pedals; a control valve connected to said pneumatically operated means for controlling the operation of the same; and a connection between said simulated rudder pedals and said control valve for operating said control valve upon movement of said simulated rudder pedals from a predetermined neutral position for causing said pneumatically operated means to exert through its connection with said simulated rudder pedals a force upon the simulated rudder pedals .opposite the direction of movement thereof.

5. In a grounded flying training device of the type including a simulated fuselage having a seat for a student, the combination of a member simulating a flightcontrol member of actual aircraft positioned near said seat; a pair ,of bellows connected to said flight control simulating member; control valve means connected to each of said pair of bellows and a pneumatic source connected to said control valve means; and means operated by a movement of said flight 26 control simulating member in one direction from a predetermined neutral position for operating said valve means to connect said pneumatic source with one of said bellows and for operating said valve means to connect said pneumatic source with the other of said bellows upon a movement of said flight control simulating member in the opposite direction from said predetermined neutral position.

6. In a grounded flying training device of the type including a simulated fuselage having a seat for a student, the combination of a member simulating a flight control member of actual aircraft; a bellows connected to said flight control simulating member; a control valve connected to said bellows and a pneumatic source arranged to be connected to said bellows through said valve according to the position of said valve; and connecting means between said flight control simulating member and said valve operated by a movement of said flight control simulating member in one direction from a predetermined neutral position for operating said valve to connect said pneumatic source with said bellows and for operating said valve to vent said bellows to the atmosphere upon a movement of said flight control simulating member in the opposite direction from said predetermined neutral position.

7. In a grounded flying training device of the type including a simulated fuselage having a seat for a student, the combination of a manually movable member simulating a flight control of an actual aircraft positioned near said seat; a fluid-operated member connected to said flight control simulating member; a valve connected to said fluid-operated member so that when said valve is in a predetermined neutral position said fluid-operated member is neutralized; a fluid source connected to said valve; and a connection between said flight control simulating member and said valve so that when a manual force is applied to said flight control simulating member to move the same from a predetermined neutral position said valve is positioned to operate said fluid-operated member to exert a force upon said flight control simulating member in the direction opposite the manual movement thereof, and when said manual force is removed said fluid-operated member returns said flight control simulating member and said valve to said predetermined neutral position.

8. In a grounded flying training device of the type including a simulated fuselage having a seat for a student, the combination of a member simulating a flight control of an actual aircraft positioned near said Seat; a pair of bellows connected to said flight control simulating member; a reversible control valve connected to said bellows for controlling the operation of the same; a source of vacuum connected to said control valve; and a connection between said flight control simulating member and said control valve for operating said control valve upon movement of said flight control simulating .member in one direction from a predetermined neutra1 position to admit vacuum to one of said pair of bellows and for operating said control valve upon movement of said flight control simulating member in the opposite direction from said predetermined neutral position to admit vacuum to the other of said bellows.

9. In a grounded flying training device of the type including a simulated fuselage having a seat for a student, the combination of a member simulating a flight control of an actual aircraft positioned near said seat; a pair of bellows connected to said flight control simulating member; a source of vacuum connected to a control valve, said control valve also having a connection to each of said pair of bellows and a port communicating with the atmosphere; and a connection between said flight control simulating member and said control valve for operating said control valve upon movement of said flight control simulating member in one direction from a predetermined neutral position to admit vacuum to the first of said pair of bellows and atmosphere to the second and for operating said control valve upon movement of said flight control simulating member in the opposite direction from said predetermined neutral position to admit vacuum to the second of said pair of bellows and atmosphere to the first of said pair of bellows.

10. In a grounded flying training device the combination of a simulated fuselage rotatably mounted with respect to a stationary base and having a seat for a student; a pair of simulated rudder pedals positioned near said seat; pneumatically operated means connected to said imulated rudder pedals; a first control valve connected to said pneumatically operated means for controlling the operation of the same; a second control valve in said fuselage for Controlling the rotation thereof with respect to said stationary base; and a connection between said rudder pedals and each of said control valve so that said first mentioned control valve is positioned to operate said pneumatically operated means and said second control valve is positioned to control the rotation of said fuselage according to the positions of said simulated rudder pedals.

11. In a grounded flying training device the combination of a simulated fuselage .mounted upon a universal joint for banking and having a seat for a student; a member in said fuselage near said seat simulating the banking control in an actual aircraft; pneumaticahy operated means connected to said simulated banking control; a first controlvalve connected to said pneumatically operated means for controlling the operation of the same; a second control valve in said fuselage for controlling the banking thereof; and a connection between said simulated banking control and each of said control valves so that said first mentioned control valve is positioned to operate said pneumatically operated means and said second control valve is positioned to control the banking position of said fuselage according to the position of said simulated banking control.

12. In a grounded flying training device the combination of a simulated fuselage mounted upon a universal joint for pitching and having a seat for a student; a member in said fuselage near said seat simulating the pitching control in an actual aircraft; pneumatically operated means connected to said simulated pitching control; a first control valve connected to said pneumaticaL 1y operated means for controlling the operation of the same; a second control valve in said fuselage for controlling the pitching thereof; and a connection between said simulated pitching control and each of said control valves so that said first mentioned control valve is positioned to operate said pneumatically operated means and said second control valve is positioned to control the pitching position of said fuselage according to the position of said simulated pitching control.

13. In a grounded aviation training device the combination of a simulated fuselage having a seat from a student; a manually operable member simulating a flight control member of an actual aircraft positioned near said seat; a pneumatically operated member connected to said flight control simulating member; a control valve connected to said pneumatically operated member for controlling th operation of the same; a connection between said flight contro1 simulating member and said control valve for operating said control valve upon movement of said flight control simulating member in either direction from a predetermined neutral position for causing said pneumatically operated member to exert through its connection with said flight control simulating member a force upon said flight control simulating member in the direction opposite the direction of movement of said flight control simulating member; and a manually operable member simulating a control surface trimming control of an actual aircraft connected to said control valve for operating the same to relieve the force exerted upon said flight control simulating member by said pneumatically operated member when said flight control simulating member is held in a position removed from said predetermined neutral position.

14. In a grounded aviation training device the combination of a fuselage having a seat for a student; a manually operable member simulating the banking control member of an actual aircraft positioned near said seat; a pneumaticallyoperated member connected to said banking control simulating member; a control valve connected to said pneumatically operated member for controlling the operation of the same; a connection between said banking contro1 simulating member and said control valve for operating said control valve upon movement of said banking control simulating member in either direction from a predetermined neutral position for causing said pneumatically operated member to exert through its connection with said banking contro1 simulating member a force upon said banking control simulating member in the direction opposite the direction of movement of said flight control simulating member; and manually operable means simulating the aileron trimming means of actual aircraft connected to said control valv for operating the same to relieve the force exerted upon said banking control simulating member by said pneumatically operated member when said banking control simulating member is held in a position removed from said predetermined neutral position.

15. In a grounded aviation training device the combination of a fuselage having a seat for a student; a manually operable member simulating the pitching control member of an actual aircraft positioned near said seat; a pneumatically operated member connected to said pitching control simulating member; a control valve connected to said pneumatically operated member for controlling the operation of the same; a connection between said pitchin contro1 simulating member and said control valve for operating said control valve upon movement of said pitching control simulating member in either direction from a predetermined neutral position for causing said pneumatically operated member to exert through its connection with said pitching control simulating member a force upon said pitching control simulating member in the direction opposite the direction of movement of said flight control simulating member; and a manually operable member simulating the elevator trimming means of actual aircraft connected to said control valve for operating the same to relieve the force exerted upon said pitching control simulating member by said pneumatically operated member when said pitching control simulating member is held in a position removed from said predetermined neutral .position.

16. In a grounded aviation training device the combination of a fuselage having a seat for a student; a pair of rudder pedals simulating the rudder pedals of a real plane positioned near said seat; pneumatically operated means connected to said simulated rudder pedals; a control valve connected to said pneumatically operated means for controlling the operation of the same; a connection between said simulated rudder pedals and said control valve for operating said control valve upon movement of said rudder pedals from predetermined neutral positions for causing said pneumatically operated means to exert through its connection with said rudder pedals a force upon the rudder pedals in the direction opposite the direction of movement thereof; and a manually operable member simulating the rudder trimming means of actual aircraft connected to said control valve for operating the same to relieve the force exerted upon the rudder pedals when they are held in positions removed from the predetermined neutral position.

1'7. In a grounded aviation training device the combination of a fuselage having a seat for a student; a manually operable member simulating a flight control member of actual aircraft positioned near said seat; a pair of bellows connected to said flight control simulating member; ontrol 'valve means connected to each of said pair of bellows and a pneumatic source connected to said control valve means; means operated by a movement of said flight control simulating member in one direction from a predetermined neutral position for operating said valve means to connect said pneumatic source with one of said bellows and for operating said valve means to connect said pneumatic source with the other of said bellows upon a movement of said flight control simulating member in the opposite direction from said predetermined neutral position; and a manually operable member simulating a control surface trimming member of an actual aircraft connected to said control valve means for operating the same.

18. In a grounded aviation training device the combination of a manually operable member simulating a flight control member of actual aircraft; a bellows connected to said flight control simulating member; a control valve connected to said bellows and a pneumatic source arranged to be connected to said bellows through said valve according to the position of said valve; means operated by a movement of said flight control simulating member in one direction from a predetermined neutral position for operating said valve to connect said pneumatic source with said bellows and for operating said valve to vent said bellows to the atmosphere upon a movement of said flight control simulating member in the opposite direction from said predetermined neutral position and a manually operable member simulating a control surface trimming means of actual aircraft connected to said valve for operating the same.

19. In a grounded aviation training device including a fuselage having a seat for a student, the combination of a member simulating a flight control member of an actual aircraft positioned near said seat; a pair of bellows connected to said flight control simulating member; a control valve connected to said bellows for controlling the operation of the same a source of vacuum connected to said control valve; a connection between said flight control simulating member and said control valve for operating said control valve upon movement of said flight control simulating member in one direction from a predetermined neutral position to admit vacuum to one of said pair of bellows and for operating said control valve upon movement of said flight control simulating member in the opposite direction from said predetermined neutral position to admit vacuum to the other bellows; and a manually operable member simulating a control surface trimming control of an actual aircraft connected to said control valve for regulating the passage of vacuum through said valve to said bellows.

20. In a grounded aviation training device including a simulated fuselage having a seat for a student, a member simulating a flight control of an actual aircraft positioned near said seat; a pair of bellows connected to said flight control simulating member; a source of vacuum connected to a control valve, said control valve also having a connection to each of said bellows and a port communicating with the atmosphere; a connection between said flight control simulating member and said control valve for operating said valve upon movement of said flight control simulating member in one direction from a predetermined neutral position to admit vacuum to the first of said pair of bellows and atmosphere to the second and for operating said control valve upon movement of said flight control simulating member in the opposite direction from said predetermined neutral position to admit vacuum to the second of said pair of bellows and atmosphere to the first; and a manually operable member simulating a control surface trimming control of an actual aircraft connected to said control valve for regulating the passage of vacuum and air to said bellows.

21. In a grounded aviation training device including a fuselage having a seat for a student, the combination of a member simulating a flight control member of an actual aircraft positioned near said seat; a pair of bellows connected to said flight control simulating member; a control valve connected to a pneumatic source, said control valve having two relatively movable leaves; a pneumatic connection between said valve and each of said bellows; a manually operable member inside said fuselage; and mechanical connections from said flight control simulating member and said manually operable member to said valve for differentially positioning the relatively movable leaves of said valve.

KARL A. KAIL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,316,181 Ocker 'Apr. 3, 1943 2,341,253 West Feb. 8, 1944 2,358,016 Link Sept. 12, 1944 2,358,018 Lowkrantz Sept. 12, 944 2,385,095 McCarthy Sept, 18, 1945 2,396,660 Kanter Mar. 19, 1946 2,450,261 West Sept. 28, 1948 

